| Technical Specification | ||||
| Filesystem library(filesystem TS) | ||||
| Library fundamentals(library fundamentals TS) | ||||
| Library fundamentals 2(library fundamentals TS v2) | ||||
| Library fundamentals 3(library fundamentals TS v3) | ||||
| Extensions for parallelism(parallelism TS) | ||||
| Extensions for parallelism 2(parallelism TS v2) | ||||
| Extensions for concurrency(concurrency TS) | ||||
| Extensions for concurrency 2(concurrency TS v2) | ||||
| Concepts(concepts TS) | ||||
| Ranges(ranges TS) | ||||
| Reflection(reflection TS) | ||||
| Mathematical special functions(special functions TR) | ||||
| Experimental Non-TS | ||||
| Pattern Matching | ||||
| Linear Algebra | ||||
| std::execution | ||||
| Contracts | ||||
| 2D Graphics |
| Classes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Functions | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| File types | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <experimental/filesystem> | ||
void resize_file(const path& p,std::uintmax_t new_size); void resize_file(const path& p,std::uintmax_t new_size, error_code& ec); | (filesystem TS) | |
Changes the size of the regular file named byp as if by POSIXtruncate: if the file size was previously larger thannew_size, the remainder of the file is discarded. If the file was previously smaller thannew_size, the file size is increased and the new area appears as if zero-filled.
Contents |
| p | - | path to resize |
| new_size | - | size that the file will now have |
| ec | - | out-parameter for error reporting in the non-throwing overload |
(none)
On systems that support sparse files, increasing the file size does not increase the space it occupies on the file system: space allocation takes place only when non-zero bytes are written to the file.
Demonstrates the effect of creating a sparse file on the free space.
#include <experimental/filesystem>#include <fstream>#include <iostream>namespace fs= std::experimental::filesystem; int main(){ fs::path p= fs::temp_directory_path()/"example.bin";std::ofstream(p).put('a');std::cout<<"File size: "<< fs::file_size(p)<<'\n'<<"Free space: "<< fs::space(p).free<<'\n'; fs::resize_file(p,64*1024);// resize to 64 KBstd::cout<<"File size: "<< fs::file_size(p)<<'\n'<<"Free space: "<< fs::space(p).free<<'\n'; fs::remove(p);}
Possible output:
File size: 1Free space: 31805444096File size: 65536Free space: 31805444096
| returns the size of a file (function)[edit] | |
| determines available free space on the file system (function)[edit] |
